The present invention relates to a hybrid system and a power control unit capable of producing constant power using a wind-power generator and a battery energy storage system.
Recently, it has been urged to introduce power generators employing natural energy such as a wind-power generator and a photovoltaic power generator. However, output power from these generators varies depending on natural conditions. There hence exists a fear that in association with increase in the power produced by the generators using natural energy, power systems receiving the power are adversely influenced as a result. For example, there may occur a frequency variation and a voltage variation. To cope with the difficulty, there has been proposed a method in which a battery energy storage system is installed for use with a natural-energy power generator to thereby suppress or to control the variation in output power of the generator.
The hybrid system using wind power or energy and a battery includes a wind-power generator to produce output power variable according to a change in the wind speed and a battery energy storage system to control variation in the output power of the generator. The hybrid system supplies the output power thus controlled to power systems.
JP-A-2001-327080 describes a method in which an output target value is set according to a charge capacity of a battery. JP-A-2006-141093 describes a method in which in order to set charge capacity of a battery to a target value, a charge-discharge command value of a battery energy storage system is changed according to the charge capacity, the charge-discharge command value being obtainable using the difference between an output value and an average value of a wind-power generator.